Cardiac resynchronization therapy (CRT) is a treatment for heart failure patients in which one or more heart chambers are electrically stimulated (paced) to restore or improve heart chamber synchrony. Improved heart chamber synchrony is expected to improve hemodynamic performance of the heart, such as assessed by ventricular pressure and the rate of change in ventricular pressure or other hemodynamic parameters, thereby alleviating symptoms of heart failure. Achieving a positive clinical benefit from CRT is dependent on several therapy control parameters, such as the atrio-ventricular (AV) delay and the inter-ventricular (VV) delay. The AV delay controls the timing of ventricular pacing pulses relative to an atrial depolarization, intrinsic or paced. The VV delay controls the timing of a pacing pulse in one ventricle relative to a paced or intrinsic sensed event in the other ventricle.
Numerous methods for selecting optimal AV and VV delays for use in controlling CRT pacing pulses have been proposed. For example, clinicians may select an optimal AV or VV delay using Doppler echocardiography or other imaging modalities to optimize a hemodynamic variable. Such clinical techniques are time-consuming, require an expert technician to perform, and are performed at a discreet time, such as at device implantation or during a clinical visit, without ongoing adjustment to the CRT therapy parameters as the need may arise. Other methods may be based on a hemodynamic sensor signal or a sensor of mechanical heart function. Such methods may require additional sensors and therefore add cost to the overall system. A need remains, therefore, for a device and method that enables closed loop optimization of CRT therapy parameters for restoring ventricular synchrony and alleviating the symptoms of heart failure associated with ventricular dyssynchrony.